Fuel Injector 4 Circuit Malfunction

I had the valve cover gasket replaced on my 2006 4 cylinder Tacoma and soon after the check engine light came on. OBDII was complaining about a fuel injector 4 circuit malfunction. The only thing I could find is what I believe is a problem with the wire harness. The factory wiring diagram shows the power for the injectors comes from the ignition switch via the fuse / junction box in the engine compartment. From the fuse / junction box, a Black / Red wire runs to injector #1, and then is spliced off to the other 3 injectors. Using an ohm meter, I checked continuity from the fuse box connector to injector #1. According to the wiring diagram, I should read close to zero ohms. I am reading 1 to 2 kilo ohms instead. I have seen 3 different wiring diagrams and they all indicate a direct connection which should be close to zero ohms. Have I found the problem, or am I missing something? I want to be sure before I go tearing onto the wiring harness. Any advice would be greatly appreciated. Thanks!

 

Does your truck have a 2.4 L engine? I thought they were 2.7L engines? Might want to correct.

 

The BLK/RD is the power supply for all the injectors, does the truck run now?
Next thing to do is Ohm the suspect injector itself and compare that reading to the other 3 good injectors.
If they are the same, swap that suspect injector with a know good injector and see if your code moves with the injector (I'm guessing P0354?)
If the code does not move with the injector, then you need to trace the GREEN wire back to the PCM and make sure it is not damaged (shorted or OPEN).
The injectors are ground side switched by the PCM and the driver for no. 4 may have gone south on you.

 

It should be as you stated a straight wire between the connector block and the injector harness.

What do you see at the other injectors Ohm wise?

Does the truck run at all?

 

It's the 4 cylinder engine. The engine runs great. The problem is intermittent. I am very suspicious of the high ohm reading from the junction block to the first splice in the injector 12 VDC power wiring...

 

I have good continuity between the 12VDC connections between the injectors, it's just the high ohm reading between injector #1 and the junction box. I'm pretty sure that splice is bad...

 

The section of wire with high ohms reading is likely the problem. Hook up the meter again like you described and do the wiggle test! You should be able to narrow down the section/area with the intermittent high resistance. Then split the insulation apart and look for some damaged wiring

Sometimes though, if the dmm leads are not making good contact you can get a false high ohms reading. Honestly, it's much more likely that the #4 injector connector is not pushed on all the way, or the pins may be damaged /backing out

 

I have completely checked out the wiring harness for the fuel injector circuits. I did not find any problems. I cleaned all of the contacts that I could, and re-seated all connectors. I measured the resistance of all 4 injectors - they all measured between 14.2 ohms and 14.4 ohms. I put it all back together, and after 2 days, the P0204 code came back. I have noticed an occasional rough running while idling. I am now suspecting fuel injector #4. I am thinking of replacing injector 4. Or, I could swap injectors and see if the code follows the injector. Is this hard to do? I've never messed with fuel injectors. I also read that a clogged injector can cause the error code and adding injector cleaner to the fuel might fix it.

Any suggestions or comments?

Also, any recommendations for a handheld OBDII monitor? I am currently using my desktop computer...

 

I use a BAFX obd2 that connects to my android phone via bluetooth. I use the Torque Pro app with it. The BAFX is Less than $25. The app costs about $6-7. Can buy the BAFX on Amazon.

 

You can swap injectors the same as swapping ignition coils. The injector o-rings can be re-used if you're careful with them. I use a little di-electric grease to help them slip back in and seat properly

 

I am going to replace the injector. OEM or aftermarket part? Which aftermarket part would be recommended?

 

No aftermarket, OEM only.

 

So I have my new OEM fuel injector. It looks like I need to remove all 4 injectors with the fuel rail, pull off #4 injector, install new one on fuel rail, and reinstall rail/injectors. It sounds easy, but I've never done it before. Any hints or suggestions? I would greatly appreciate any comments. Thanks!

 

Did you get 3 new additional Orings for the injectors you're not replacing?
If not, your asking for a leak.
Pull the rail straight up and out, use some petroleum jelly on the new injector Orings (just a dab).
Then push them into place.
Don't forget to release the fuel pressure first.

 

Thanks! I will be ordering new Orings for the 3 old injectors. Are there any other O rings or gaskets I will need, like the fuel line connections?

 

I'm a loser. Replaced fuel injector #4. Drove for 2 days with no CEL. 3rd day I started it up and there was the CEL. P0204 and a C0104. As far as I know, the only thing left is the ECM. I give up.

 

So I just got my Tacoma back from the shop. Their OBD Scanner did not find the P0204 code at all. Instead, they got codes P2445, P0455, P2441, and P0441. Root cause - disconnected vacuum line to air injection valve. My OBD reader totally sucks. That's my expensive lesson. On the bright side, they found my fuel cap was leaking badly...

 

Hey at least you got it sorted out! Having to go to the dealer for a little diag and a new cap ain't so bad, it could have been worse..

 

Thanks b_r_o! Always look on the bright side of life!

 

The saga continues... Turns out that my code reader is OK. I replaced the injector, but missed reconnecting a vacuum line. This led to the CEL coming back on with the new codes. The injector was indeed bad, and replacing it cleared the injector fault code. Reconnecting the vacuum line and a new gas cap made it all better, for 1 week. While driving to work, the CEL came back on with a vengeance - flashing rapidly. The engine was misfiring and shaking like crazy. Back to the shop. Bad ignition coil. Picked it up yesterday, and everything was fine. This morning when I started her up, the low tire pressure light came on. I'm getting too old for all of this crap...